There is often a need to determine the transmissive or reflective properties of an object. The color of a sample can be determined by measuring its transmittance or reflectance properties at different wavelengths. For example, it is known to measure light that has been reflected from or transmitted through an object at wavelengths from 400 nm to 700 nm, typically at 10 nm intervals. However, to obtain accurate measurements of the spectrum of an object, a color sensor must have sufficient wavelength channels. Sensors with many wavelength channels (typically 31) produce highly accurate measurements but have cost and complexity drawbacks. Conversely, a sensor with few wavelength channels will lose some of the measurement fidelity and produce a less accurate measurement. Specifically, when the number of wavelength channels are limited, the color information obtained will be less accurate.
In cases of low measurement fidelity, a series of known transmittance or reflectance color standards can be measured, and matrix transformation can be usually used to recover the transmittance or reflectance of the specimen. However, using such matrix transformation will always introduce error that yields less than satisfactory results.
For example, commonly owned U.S. Pat. No. 8,532,371, the contents of which are herein incorporated by reference in its entirety, teaches use of an RGB camera in conjunction with three (3) intermittent light sources to generate nine (9) effective channels. The U.S. Pat. No. 8,532,371, describes estimating from three (3) spectral channels of the spatial pixels, a tristimulus values.
However, what is needed in the art is a system, method and apparatus that utilizes more than three (3) spectral channels to determine or estimate spectra values, not tristimulus values.
Thus, what is needed in the art is a system that improves upon and advances the technological field of color identification. For example, what is needed are systems and methods that utilize multiple known illuminants to improve measurement data such that the end results provide a more precise color measurement value for an object under analysis. Furthermore, what is needed in the art are systems and methods to improve the measurement obtained using sensors having few wavelength channels.
What is also needed is a solution to the problem introduced by using matrices to correct for inaccuracy of estimation due to a low number of measurement channels.